Fallow histories: Effects on nitrogen contribution, growth and yield of plant and ratoon crops of sugarcane

This paper summarises the results of four experiments involving fallow legumes. First, results of legume demonstration areas established at a number of grower sites in north Queensland are discussed. The areas clearly demonstrate that the experimental results achieved with well managed soybean fallows can be repeated in commercial situations. Second, the effects of fallow history on the cane and sugar yield of a first ratoon crop of variety Q138 grown at the Sugar Yield Decline Joint Venture sub-station at Feluga are reported. These results indicate that there is a carry-over of beneficial effects from soybean and peanut fallow into the first ratoon sugarcane crop. Third, data are presented that characterise the mineralisation and movement of legume nitrogen following legume incorporation. Fourth, the plant cane yields from an experiment in which four rates of nitrogen fertiliser were applied to variety Q120 fOllowing either a well managed soybean fallow Or a farmer fallow are reported. These results indicate that soil type and climatic conditions during the fallow period are likely to influence the residual value of the fallow in terms of promoting cane and sugar yield.